1. Field of the Invention
Method and arrangement for multiplexing a multiplicity of digital data streams to form a digital overall data stream, as well as a method and arrangement for demultiplexing a digital overall data stream to form a multiplicity of digital data streams.
2. Description of the Related Art
In the field of multimedia, a very wide range of types of digital data streams in some form have to be transmitted jointly. It is intended to make the influence of transmission errors which occur frequently during the transmission as imperceptible as possible for a user of a system which decodes the transmitted data and makes said data available to the user.
The term digital data streams in the following text is not intended in any way to mean, in the final analysis, digital data which can normally be processed into data packages of predeterminable size, that is to say with a predeterminable number of bytes.
Digital data with which text is described, for example a text file,
audio data,
video data, or
digital control data for controlling any given technical system.
To this end, it is known from the document [1] for a measure to be provided for error identification and/or error correction for the data streams, and for the data streams to be multiplexed to form an overall data stream. It is in this case furthermore known from [1] for the measure for error identification and/or error correction to be carried out separately for each data stream which it is intended to transmit.
The term measure for error identification and/or error correction means, in the following text, a method by means of which it is possible to identify and/or to correct errors which occur in the transmission of a data stream.
A very wide range of principles of measures for error identification and/or error correction are known, for example so-called repetition requirement methods (Automatic Repeat Request methods, ARQ Type I, ARQ Type II) or else so-called methods for forward error correction. In the context of methods for forward error correction, a distinction is drawn between methods which identify errors and methods which correct errors.
The known procedure results primarily in the disadvantage of considerable inefficiency since a large element of header information is required, as well as information which is required for error identification and/or error correction. This problem increases severely as the number of data streams to be multiplexed and to be transmitted increases. The problem can even become so large that, beyond a certain number of data streams to be multiplexed, depending on the size of the data packages, no information whatsoever would be transmitted via the data streams, but only header information or information for error identification and/or error correction.
An arrangement is known from [4], in which a data stream is split into 3 data stream elements (wanted information, specific monitoring information, general monitoring information). The same error correction method is carried out for each of the 3 data stream elements.
[5] describes an image transmission unit in which a video data stream and an audio data stream are subjected separately to the same error correction method.
The invention is based on the problem of specifying methods and arrangements for multiplexing and demultiplexing data streams, by which means a more efficient measure for error identification and/or error correction is possible than was possible with the known method.
In accordance with one aspect of the invention, the data streams are grouped to form at least two digital intermediate data streams. The grouping is carried out in such a way that identical data streams (DS) are grouped jointly to form an intermediate data stream (ZDS) and different data streams (DS) are grouped into different intermediate data streams (ZDS). A measure for error identification and/or error correction of the intermediate data streams is carried out for the intermediate data streams, and the intermediate data streams are grouped to form the overall data stream.
In accordance with a further aspect of the present invention, the overall data stream is grouped to form at least two digital intermediate data streams. The grouping is carried out in such a manner that identical data streams (DS) are jointly grouped to form an intermediate data stream (ZDS) and different data streams (DS) are grouped into different intermediate data streams (ZDS). A measure for error identification and/or error correction of the intermediate data streams is carried out for at least one of the intermediate data streams, and the intermediate data streams are grouped into the data streams.
The arrangement for multiplexing a multiplicity of digital data streams to form an overall data stream has a first grouping stage with at least two first grouping units by means of which the data streams are grouped to form at least two digital intermediate data streams. The grouping is carried out in such a manner that identical data streams (DS) are jointly grouped to form an intermediate data stream (ZDS), and different data streams (DS) are grouped into different intermediate data streams (ZDS). A means for error identification and/or error correction of the intermediate data streams is in each case provided for at least one of the intermediate data streams. Furthermore, a second grouping stage is provided with a second grouping unit by means of which the intermediate data streams are grouped to form the overall data stream.
The arrangement for demultiplexing a digital overall data stream to form a multiplicity of digital data streams likewise has a second grouping stage with a second grouping unit, by means of which the overall data stream is grouped to form at least two digital intermediate data streams. The grouping is carried out in such a manner that identical data streams (DS) are jointly grouped to form an intermediate data stream (ZDS), and different data streams (DS) are grouped into different intermediate data streams (ZDS). Furthermore, a means for error identification and/or error correction of the intermediate data streams is provided for at least one of the intermediate data streams. A first grouping stage is also provided, having at least two first grouping units, by means of which the intermediate data streams are grouped to form the data streams.
Both the methods and the arrangements have the advantage that more efficient error identification and/or error correction is possible. As is explained in the following text, the level of efficiency of error identification and/or error correction also rises with a rising number of data streams for which error identification and/or error correction is intended to be carried out.
In a development, an advantageous feature of both the methods and the arrangements is that data streams which represent similar requirements in terms of a required error identification and/or error correction are grouped jointly into in each case one intermediate data stream.
In this way, a grouping is achieved which is matched to the respective requirement for error identification and/or error correction for a group of data streams, which allows very efficient error identification and/or error correction.
This advantage is furthermore reinforced by the fact that error identification and/or error correction matched to the respective requirements are/is provided for intermediate data streams, in a development.
In a development, it is furthermore advantageous to use an error-proof method in the second grouping stage and/or in the grouping of the intermediate data streams into the overall data stream and/or in the grouping of the overall data stream into the intermediate data streams. This development results in further protection of the transmission of the overall data stream, which leads to a further efficiency improvement in the methods and the arrangements.
In order to improve the reliability of the method, it is advantageous to carry out an initialization phase at the start of the method, the initialization phase being carried out using a data channel, which has good error protection and is provided by the multiplexer, for the transmission of the data via the transmission medium xc3x9cM.
A further improvement is achieved in that data streams for which no error identification and/or error correction are/is required are not considered in the grouping into the intermediate data streams, and the latter are directly grouped with the intermediate data streams to form the overall data stream. This development leads to a saving in terms of methods for error identification and/or error correction for data streams for which no error identification and/or error correction are/is actually required. This leads on the one hand to a saving in computation time requirement for carrying out the method with a computer and, on the other hand, for example to a saving of multiplexers.